1. Field of the Invention
The present invention relates to a cycloidal gear, and in particular to a cycloidal gear with a small number of teeth, which is used as a pinion, or a small diameter gear, of a gear, or large diameter gear, and the pinion constituting a reduction gear mechanism.
2. Description of the Related Art
Conventionally, a gear with involute tooth has been used as a gear, and a gear train has been constituted by combining a gear with the involute tooth and a pinion therewith. When gear ratio is intended to be increased by reducing the tooth number of the pinion, undercut occurs at a deddendum of the pinion. As a method for solving the undercut, a shift method has been proposed, but, when the tooth number of the pinion is reduced, strength and durability thereof deteriorate remarkably. Therefore, the pinion is required to have six or more teeth in practical use. Assumed that the tooth number of a pinion is denoted by Z1 and the tooth number of a gear is denoted by Z2, the gear ratio is represented by Z2/Z1.
On the other hand, a logix gear (for example, refer to Japanese Patent Application Publication (JP-B) No. 2-15743) has been developed in recent years. In the logix gear, a tooth has been formed by connecting a plurality of involute curves of micro-distances to one another in a continuously curved manner. For this reason, when the logix gear is used, the shape of a tooth can be designed in a various manner. According to this design, a pinion can be obtained which does not cause any problem regarding its strength even when the pinion has only four teeth, thereby making it possible to develop a gear train of a high gear ratio.
However, there occurs a problem that, when a gear or a pinion to which the logix gear is applied is designed, calculations for connecting a remarkable number of involute curves to one another continuously are repeated many times for various tooth shapes, so that much time is required to complete the design of the gear or the pinion.